Vertical-drop grain aspirator

Abstract

An aspirator and method for separating fines and foreign matter from dry, free-flowing granular material, characterized by a vertical drop of the unclean granular material in a separation plenum into an opposing upward air stream and a plurality of vertically-spaced, horizontally-extending transverse air streams. Suspended fines and foreign matter are conducted from the granular material in the separation plenum through a plurality of vertically-spaced outlets into a manifold for discharge from the aspirator. The apparatus and method avoid bunching, recompaction and congregating of the granular material during the separation process, to thereby increase throughput and optimize separation efficiency.

Having thus described our invention, we claim: 
     
       1. A vertical-drop aspirator for separating fines and/or foreign matter from dry, free-flowing, granular material, which comprises: a. a charging hopper,   b. discharge means for conducting said granular material from said aspirator, disposed substantially vertically beneath said charging hopper,   c. a separation plenum formed by spaced side walls and spaced end walls contiguous with said side walls extending vertically downwardly from said charging hopper to said discharge means, and adapted to communicate with said charging hopper and said discharge means, to thereby conduct said granular material from said charging hopper vertically downwardly in an unimpeded, free-fall, vertical flow path to said discharge means,   d. an air outlet manifold extending substantially the entire length of said separation plenum adjacent one side wall thereof,   e. a plurality of horizontally-extending, vertically-spaced air inlets formed in the side wall of said separation plenum opposite said air outlet manifold, providing inlets into said separation plenum,   f. a corresponding plurality of horizontally-extending, vertically-spaced air outlets formed in the side wall of said separation plenum opposite said air inlets and adjacent said air outlet manifold, providing outlets from said separation plenum to said air outlet manifold and disposed opposite and above said air inlet passages, respectively, and   g. a separation plenum outlet lip depending from said side wall of said separation plenum adjacent said air outlet manifold at the upper periphery of each of said vertically-spaced air outlets, extending downwardly and into said separation plenum and terminating above and spaced horizontally from said air inlet passage immediately below and opposite said air outlet passage.   
     
     
       2. The aspirator of claim 1 and a separation plenum inlet depending from said side wall of said separation plenum opposite said air outlet manifold at the upper periphery of each of said vertically-spaced air inlets, extending downwardly and into said separation plenum and terminating below and spaced horizontally from said separation plenum outlet lip above the lower periphery of said air inlet passage. 
     
     
       3. The aspirator of claim 2 and an air inlet lip depending from side wall of said separation plenum opposite said air outlet manifold at the lower periphery of each of said air inlets, extending upnwardly and terminating below the upper periphery of said air inlet passage. 
     
     
       4. The aspirator of claim 1 and an air inlet lip depending from said side wall of said separation plenum opposite said air outlet manifold at the lower periphery of each of said air inlets, extending upwardly and terminating below the upper periphery of said air inlet passage. 
     
     
       5. The aspirator of claim 4 and gate means disposed between said charging hopper and the upper end of said separation plenum for preventing communication between said separation plenum and said charging hopper except for the flow of said granular material. 
     
     
       6. The aspirator of claim 1 and gate means disposed between said charging hopper and the upper end of said seperation plenum for preventing communication between said separation plenum and said charging hopper except for the flow of said granular material. 
     
     
       7. The aspirator of claim 6 and gate means disposed below said discharge means for preventing communication between said collection hopper and the atmosphere except for the flow of said granular material. 
     
     
       8. The aspirator of claim 13 and gate means disposed below said discharge means for preventing communication between said discharge means and the atmosphere except for the flow of said granular material. 
     
     
       9. A method of seperating fines and/or foreign matter from dry, free-flowing, granular material which comprises a. dropping the material in an unimpeded, free-fall vertical flow path,   b. providing an opposing, substantially-upward air stream in said flow path throughout substantially the entire length of said flow path, to thereby suspend said fines and/or foreign matter in said air stream,   c. providing a plurality of vertically-spaced, substantially-horizontal air streams extending transversely across said flow path,   d. conducting the suspended fines and foreign matter from said flow path at a corresponding plurality of spaced points above the plurality of vertically-spaced, substantially-horizontal air streams, respectively, and offset from said flow path in the direction of said substantially-horizontal air stream immediately beneath each of said points, and   e. collecting the separated granular material, free of said fines and/or foreign matter, in said flow path below said air streams   
     
     
       10. The method of claim 9 wherein said opposing, substantially upward air stream has a velocity in the range of 600 to 1200 feet per minute. 
     
     
       11. The method of claim 10 wherein said vertically-spaced, substantially horizontal air streams have a velocity in the range of 800 to 2200 feet per minute. 
     
     
       12. The method of claim 9 wherein said vertically-spaced substantially horizontal air streams have a velocity in the range of 800 to 2200 feet per minute. 
     
     
       13. The method of claim 12 wherein said suspended fines and foreign matter are conducted from said flow path at a velocity in the range of 1000 to 2400 feet per minute. 
     
     
       14. The method of claim 9 wherein said suspended fines and foreign matter are conducted from said flow path at a velocity in the range of 1000 to 2400 feet per minute.